CN111981236A - Silencing device for actively modulating frequency and changing stop band and silencing method thereof - Google Patents

Abstract

The invention discloses a silencing device for actively modulating frequency and changing stop band, which comprises: the main line, the flexible pipe of concatenation between main line and upper reaches pipeline or low reaches pipeline, with the wave length pipe of main line intercommunication, the Helmholtz resonator, the wave length pipe, main line between the Helmholtz resonator passes through the concatenation of controllable flexible pipe, be close to upper reaches pipeline and downstream pipeline department in the main line and be equipped with sound pressure sensor respectively, sound pressure sensor's signal access all-pass filter, all-pass filter's signal inserts the controller respectively, the control signal of controller inserts motor element, motor element's output and the regulation end of controllable flexible pipe are connected. The invention measures and analyzes the noise in real time through the active control system, and changes the resonant frequency of the resonator and the stop band of the silencing device by controlling the distance between the resonant cavities, the tube length of the 1/4 wave tube and the volume of the resonant cavity of the Helmholtz resonator through the active control system.

Description

Silencing device for actively modulating frequency and changing stop band and silencing method thereof

Technical Field

The invention relates to the technical field of pipeline noise control, in particular to a silencing device for actively modulating frequency and changing stop band and a silencing method thereof.

Background

There are currently three main approaches to controlling noise: 1. attenuation from the sound source; 2. decrease from the propagation path; 3. weakened at the human ear. The suppression of noise propagation on the pipeline belongs to the attenuation of noise from a propagation path, and the elimination of noise in the pipeline by using a side branch resonator and a helmholtz resonator is a widely applied noise reduction technology, and because the structure is simple and the noise of a certain specific frequency can be effectively attenuated, the side branch resonator and the helmholtz resonator are an important means in noise control, while the resonance frequency of the side branch resonator and the helmholtz resonator is determined at the beginning of design and cannot be changed along with the change of the noise frequency, so when the excitation frequency of a noise source or a sound field is changed, the noise elimination performance of the side branch resonator and the helmholtz resonator is greatly reduced and even has no effect. When the plurality of side-branch resonators and the helmholtz resonator are periodically connected to form the noise elimination device, the noise elimination device is called a phononic crystal, and when noise passes through the noise elimination device, due to the coupling effect of bragg reflection and resonator resonance, a plurality of stop bands can be formed, but the resonance frequency of the resonators cannot be changed, so that the application is limited. The structure parameter adjustable bypass resonator and Helmholtz resonator belong to half initiative noise elimination, and control system is simple relatively, and the running cost is lower, and the executive capability is comparatively reliable, makes it more have use value than active control at present. The resonance frequency of the resonator is adjusted by changing the structural parameters of the silencer, such as the length of the pipe, the radius of the pipe and the like, so that the silencer and the silencer can be well applied to silencing engineering by combining the two.

The invention patent No. 201610555355.6 discloses a resonator composed of a film acoustic material and a helmholtz resonator, which can solve the problem of single frequency of the helmholtz resonator during operation, but the operation mode of the resonator is completed by changing the film, and the resonator belongs to passive control, namely lacks accuracy, and sometimes cannot well correspond to noise frequency.

Disclosure of Invention

The invention aims to provide a silencing device for actively modulating frequency and changing a stop band and a silencing method thereof, which solve the problems of difficult noise reduction and single resonance frequency of pipeline noise in the prior art, improve the noise reduction effect and solve the technical problem of single use of a resonator.

The invention is realized by the following modes:

the invention provides a silencing device for actively modulating frequency and changing stop band, which comprises: the main pipeline, the concatenation is in flexible pipe between main pipeline and the upper reaches pipeline or the low reaches pipeline, with the wave length pipe of main pipeline intercommunication, helmholtz resonator, between wave length pipe, the helmholtz resonator the main pipeline passes through the concatenation of controllable flexible pipe, be close to upper reaches pipeline and downstream pipeline department in the main pipeline and be equipped with sound pressure sensor respectively, sound pressure sensor's signal access all-pass filter, all-pass filter's signal inserts the controller respectively, the control signal of controller inserts motor element, motor element's output with the regulation end of controllable flexible pipe is connected.

Furthermore, the wave tube is a telescopic wave tube, and the output end of the motor assembly is connected with the adjusting end of the telescopic wave tube.

Furthermore, a rotating shaft is arranged at the middle shaft in the resonance cavity of the Helmholtz resonator from top to bottom, two arc-shaped partition plates extend from the rotating shaft to two sides, the two arc-shaped partition plates rotate oppositely through the rotating shaft to divide the resonance cavity of the Helmholtz resonator into two chambers with variable volumes, and the output end of the motor assembly is connected with the rotating shaft.

Furthermore, the telescopic pipe is an aluminum foil telescopic air pipe.

The invention also provides a silencing method of the silencing device suitable for active frequency modulation and stop band change, which comprises the following steps:

step 1: firstly, receiving a sound pressure sensor signal close to an upstream pipeline, filtering the sound pressure sensor signal by an all-pass filter, and then transmitting the sound pressure sensor signal into a controller;

step 2: the controller compares the filtered sound pressure signal with a preset signal and calculates the adjustment degree;

and step 3: the controller controls the motor assembly to adjust the length and the position of the controllable telescopic pipe, the telescopic wave pipe and the adjustable partition plate in the Helmholtz resonator according to the adjustment degree;

and 4, step 4: judging whether the sound pressure sensor signal close to the downstream pipeline is the same as the expected signal or not, and if so, ending the silencing process; and when the difference is not the same, returning to the step 1.

The invention has the advantages and beneficial effects that:

the invention measures and analyzes the noise in real time through the active control system, and changes the resonant frequency of the resonator and the stop band of the silencing device by controlling the distance between the resonant cavities, the tube length of the 1/4 wave tube and the volume of the resonant cavity of the Helmholtz resonator through the active control system. The muffler device can make the self muffling frequency and the main frequency of the noise close to or the same without replacing the rest muffling fittings. The device also overcomes the problem of single muffling frequency of the traditional resonator.

Drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic view of a retractable 1/4 wave tube device;

FIG. 3 is a schematic view of a telescopic pipe device

FIG. 4 is a schematic diagram of the internal structure of a resonant cavity;

FIG. 5 is a cross-sectional top view of a resonant cavity;

FIG. 6 is a graph showing a comparison of transmission loss before and after changing the resonator pitch in an example of the present disclosure;

FIG. 7 is a graph comparing transmission loss before and after changing the length of the 1/4 wave resonator and the volume of the resonant cavity in the disclosed example.

Detailed Description

The present invention is further illustrated by the following more detailed description of the invention, taken in conjunction with the accompanying drawings, and it is to be understood that these examples are given solely for purposes of illustration and are not intended to limit the scope of the invention, which is defined in the claims as they appear to those skilled in the art upon reading the present disclosure.

As shown in fig. 1, the muffler device of the present invention for actively adjusting frequency and changing stop band comprises two parts, one part is a pipeline part, the other part is a control part, the pipeline part comprises: an aluminum foil telescopic air pipe 17, a pipeline communicated with a telescopic wave pipe 19, a controllable telescopic pipe 18 and a pipeline communicated with a Helmholtz resonator 20 which are sequentially spliced from an upstream pipeline 21 to a downstream pipeline 22,

as shown in fig. 2, the retractable wavelength tube 19 includes a communicating tube 191 communicating with the main pipeline, a sleeve 192 sleeved on the communicating tube 191 and having a sealed upper end, a connecting rod 193 is transversely disposed in the middle of the top of the sleeve 192, another connecting rod 194 is hinged to the other end of the connecting rod 193, the other end of the connecting rod 194 is hinged to the edge of a large disc 195, the hinged point makes a circular motion along with the rotation of the large disc 195, and the small disc 196 drives the large disc 195 to rotate through a belt 197. The rotation of the small disc drives the sleeve 192 to slide up and down on the communicating tube 191 through a structure similar to a piston rod, thereby changing the length of the telescopic wave tube 19. The retractable wave tube is preferably a retractable 1/4 wave tube,

as shown in fig. 3, the controllable telescopic tube 18 is an outer telescopic tube 181 and an inner telescopic tube 182 which are sleeved together, one end of the outer telescopic tube 181 is communicated with the main pipeline, one end of the inner telescopic tube 182 is communicated with the main pipeline, an anchor point is arranged on the outer wall of the outer telescopic tube 181, one end of a connecting rod 183 is hinged with the anchor point, the other end of the connecting rod is hinged with the edge of a large disc 184, the hinged point rotates along with the large disc 184 to perform circular motion, and the small disc 185 drives the large disc 184 to rotate through a belt 186. Rotation of the small disc 185 causes the outer telescoping tube 181 to slide left and right over the inner telescoping tube 182 by a piston rod-like structure, thereby changing the length of the collapsible tube 18.

As shown in fig. 4 and 5, the helmholtz resonator 20 is a cylindrical helmholtz resonator, and is communicated with the main pipeline through a short pipe 201. Two rotating shafts 202 and 203 which are connected with one end in a rotating way and are coaxial with the central shaft are arranged at the central shaft of the Helmholtz resonator 20, the two rotating shafts can rotate independently, one side of each rotating shaft extends to form an arc-shaped partition plate 204, the two rotating shafts drive the two arc-shaped partition plates to rotate oppositely, a resonant cavity of the Helmholtz resonator is divided into two chambers with variable volumes,

the control section includes: the sound pressure sensor 1 is arranged close to an upstream pipe intersection, the sound pressure sensor 16 is arranged close to a downstream pipe intersection, the two sensors are connected with an all-pass filter 2, the all-pass filter 2 is respectively connected with a DSP (digital signal processor) controller 3 and a DPS (data processing system) controller 7, the DSP controller 3 is connected with an asynchronous motor driver 4, the asynchronous motor driver 4 is connected with an asynchronous motor 5, the asynchronous motor 5 is powered by a power supply 6, and an output shaft of the asynchronous motor 5 is connected with a central shaft of a small disk to drive the small disk to rotate so as to realize the expansion and contraction of a controllable expansion pipe 18; the DSP controller 7 is connected with an asynchronous motor driver 8, the asynchronous motor driver 8 is respectively connected with an asynchronous motor 10 and an asynchronous motor 11, the asynchronous motor 10 and the asynchronous motor 11 are powered by a power supply 9, the asynchronous motor 10 is respectively connected with the input ends of a rotating shaft 202 and a rotating shaft 203 to drive two arc-shaped partition plates 204 to rotate oppositely, the output shaft of the asynchronous motor 11 is connected with the central shaft of the small disc 196 to drive the small disc 196 to rotate, and the telescopic wave tube 19 is stretched.

The resonance frequency of the Helmholtz resonator is expressed as

According to the formula, when the cross-sectional area S and the pipe length L of the connecting pipe for connecting the resonant cavity and the main pipeline are unchanged, the volume V of the resonant cavity is changed by adjusting the rotation of the two arc-shaped baffles in the resonant cavity, so that the resonant frequency f of the resonant cavity is adjusted. The resonant frequency of the same telescopic 1/4 wave tube is formulated as

Wherein n is a natural number, and the formula shows that when the rest structural parameters are not changed, the resonant frequency f of the telescopic 1/4 wave tube is adjusted by adjusting the length l of the telescopic 1/4 wave tube.

The silencing method comprises the following steps:

step 1: firstly, receiving a sound pressure sensor signal close to an upstream pipeline, filtering the sound pressure sensor signal by an all-pass filter, and then transmitting the sound pressure sensor signal into a controller;

step 2: the controller compares the filtered sound pressure signal with a preset signal and calculates the adjustment degree;

and step 3: the controller controls the motor assembly to adjust the length and the position of the controllable telescopic pipe, the telescopic wave pipe and the adjustable partition plate in the Helmholtz resonator according to the adjustment degree;

the relation between the result of comparison between the filtered sound pressure signal and the preset signal and the degree of adjustment is determined according to actual conditions, and the degree of adjustment can be correspondingly used for controlling the motor set to rotate forwards when the filtered sound pressure signal is greater than the preset signal; when the filtered sound pressure signal is smaller than a preset signal, the adjustment degree correspondingly controls the motor set to rotate reversely, or when the filtered sound pressure signal is smaller than the preset signal, the adjustment degree correspondingly controls the motor set to rotate forwards;

and 4, step 4: judging whether the sound pressure sensor signal close to the downstream pipeline is the same as the expected signal or not, and if so, ending the silencing process; and when the difference is not the same, returning to the step 1.

As shown in fig. 6, the solid line indicates that the tuning device is turned on, when the pitch is 0.2m, and the dotted line indicates that the initial distance between the resonators is 0.1m, it is found that the resonance frequency is not changed, but the stop band is significantly changed.

As shown in FIG. 7, the solid line indicates the unopened adjustment device, the 1/4 wavelength tube length is 0.09m, and the resonant cavity volume is 0.00031229m³The resonant frequency of the resonant cavity is 502Hz, and the resonant frequency of the 1/4 wavelength resonator is 854 Hz. The dotted line indicates that the adjustment device is turned on, at which time the 1/4 wavelength tube has a length of 0.12m and the chamber has a volume of 0.00010966m³The resonance frequency of the 1/4 wave resonator is 658Hz, and the resonance frequency of the resonance cavity is 778Hz, so that the novel silencing device for actively modulating the frequency and changing the stop band shows good silencing performance under different noise frequency working conditions.

The above are merely preferred embodiments of the present invention. The present invention is capable of other embodiments, and various changes and modifications can be made by one skilled in the art without departing from the spirit and scope of the invention. All technical solutions which are formed by adopting equivalent substitutions or equivalent transformations shall fall within the protection scope of the appended claims.

Claims (5)

1. A muffler assembly for actively modulating frequency and varying stop band, comprising: the main pipeline, the concatenation is in flexible pipe between main pipeline and the upper reaches pipeline or the low reaches pipeline, with the wave length pipe of main pipeline intercommunication, helmholtz resonator, between wave length pipe, the helmholtz resonator the main pipeline passes through the concatenation of controllable flexible pipe, be close to upper reaches pipeline and downstream pipeline department in the main pipeline and be equipped with sound pressure sensor respectively, sound pressure sensor's signal access all-pass filter, all-pass filter's signal inserts the controller respectively, the control signal of controller inserts motor element, motor element's output with the regulation end of controllable flexible pipe is connected.

2. The active frequency tuning and band-stop changing muffler device of claim 1, wherein the wavelength tube is a retractable wavelength tube, and the output end of the motor assembly is connected to the tuning end of the retractable wavelength tube.

3. The active frequency tuning and stopband altering muffler device of claim 1, wherein a rotating shaft is disposed from top to bottom at a central axis within the resonance chamber of said helmholtz resonator, two arcuate baffles extend from said rotating shaft to either side, said two arcuate baffles rotate in opposite directions about said rotating shaft to divide the resonance chamber of said helmholtz resonator into two variable volume chambers, and an output of said motor assembly is connected to said rotating shaft.

4. The active tuning and stopband altering silencer of claim 1, wherein said bellows is an aluminum foil bellows.

5. A silencing method of a silencing device for actively modulating frequency and changing stop band is characterized by comprising the following steps:

step 1: firstly, receiving a sound pressure sensor signal close to an upstream pipeline, filtering the sound pressure sensor signal by an all-pass filter, and then transmitting the sound pressure sensor signal into a controller;

step 2: the controller compares the filtered sound pressure signal with a preset signal and calculates the adjustment degree;

and step 3: the controller controls the motor assembly to adjust the length and the position of the controllable telescopic pipe, the telescopic wave pipe and the adjustable partition plate in the Helmholtz resonator according to the adjustment degree;

and 4, step 4: judging whether the sound pressure sensor signal close to the downstream pipeline is the same as the expected signal or not, and if so, ending the silencing process; and when the difference is not the same, returning to the step 1.

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